Regarding assembling structures of this type, for example, a technique disclosed in Japanese Laid-Open Patent Publication No. 2001-50229 is known. A clip employed in this technique is equipped with a pair of lock members mounted to a pedestal so as to be situated on both sides of a rib of the pedestal, which is molded integrally with an attachment member, and two side walls protruding outwardly from these lock members. And, by inserting the clip mounted to the pedestal of the attachment member into a clip hole provided in the mating member, shoulder portions of the two side walls are engaged with the edge of the clip hole on the inner surface side of the mating member, whereby the attachment member is assembled to the mating member via the clip.
In the technique disclosed in Japanese Laid-Open Patent Publication No. 2001-50229, in the state in which the attachment member has been assembled to the mating member via the clip, the retention load of the clip with respect to the mating member is determined exclusively by the engaging force exerted between the edge of the clip hole and the shoulder portions of both two side walls. And, this retention load is always fixed as long as the clip and the clip hole remain the same. Thus, to change the retention load, it is necessary to employ an appropriate clip selected from among different kinds of clips, and there is a risk of a wrong clip being employed.
Therefore, there is a need in the art for enabling to select different retention loads with respect to the clip hole of the mating member with a single kind of clip, and eliminating an operational error in the step of mounting the clip to the attachment member.